An uneasy calm settled over Ferguson, Missouri, early Tuesday after a second night of violent clashes between law enforcement and residents protesting the police shooting of an unarmed black teenager, with another demonstration planned for mid-morning.

So far, more than 50 people have been arrested in protests following the death of Michael Brown, 18, in a largely black St. Louis suburb on Saturday, after what police officials said was a struggle with a gun in a squad car.

The FBI has opened a civil rights investigation into the racially charged case, and St. Louis County also is investigating the shooting.

Police have not said why Brown was in the police car. At least one shot was fired during the struggle, and then the officer fired more shots before leaving the car, police said.

Police challenged

Chanting “hands up, don't shoot,” protesters overnight challenged police trying to seal off the neighborhood where Brown was shot, a low-income, high-crime area east of downtown Ferguson. Some protesters said they were outraged that Brown appeared to have been shot while holding his hands up in surrender, calling the shooting the latest in a long history of police harassment of area minorities.

“They brought this on themselves,” said 25-year-old Adam Burcher of Ferguson, who stood outside the Ferguson Police Department on Monday night with a sign reading “Stop Killing.”

Later on Tuesday, a protest is expected outside the St. Louis County prosecutor's office in Clayton, Missouri, and officials also are expected to identify the police officer involved in the shooting.

Brown's family has hired Benjamin Crump, an attorney who represented the family of Trayvon Martin, an unarmed black teenager whose fatal shooting in Florida by a neighborhood watch volunteer in 2012 triggered nationwide protests.

“To bring further calm, and for people to have confidence, we need the Justice Department to take over this investigation completely and not rely on the St. Louis police,” Crump told CNN in an interview on Tuesday.

Brown's parents have called for calm, but demonstrations have turned violent. More violence ensued on Monday night as officers in riot gear, armed with rifles and accompanied by dogs tried to secure the area.

Some protesters said they were trying to honor Brown's memory. A memorial of flowers, notes and candles grew near the apartment building where Brown reportedly was walking to see his grandmother before he became involved with police.

“We aren't going to let this one go,” said 18-year-old Dreya Harris of St. Louis. “People feel like in the Trayvon Martin case that there was no justice.”

Investigation underway

Ferguson Police Chief Tom Jackson has said officers are determined to keep a lid on the simmering tensions.

The expected announcement identifying the officer involved in the shooting also could escalate tensions in an area that has seen a stark demographic shift in recent decades.

Officials, who so far have not disclosed the officer's race, have said the six-year police veteran is on administrative leave pending the investigation. About two-thirds of Ferguson's 21,000-strong population are black, while 50 of the 53 members of its police department members are white.

Most of the communities around Ferguson have gone from white to mostly black in the last 40 years, said Terry Jones, political science professor at University of Missouri-St. Louis.

“There's a long history of racial injustice,” said Jones. “Slowly and not so surely, the St. Louis metropolitan area has been trying to figure out a way forward. As the Michael Brown shooting indicates, there are often setbacks.”